Spring Data JPA 系列 —— 两张表（多对多关联）

JPA

前提

表结构

例子

创建 Maven 项目

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>

<groupId>org.lewis.demos</groupId>
<artifactId>jpa-manytomany-springboot-h2</artifactId>
<version>1.0</version>

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.2.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>

<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>

<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>

<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>

</project>

src/main/resources/application.properties

## DATASOURCE Settings
#spring.datasource.driver-class-name:org.h2.Driver
#spring.datasource.password:demo
#spring.datasource.url:jdbc:h2:tcp://127.0.0.1/~/jpa-h2
#spring.datasource.username:demo
## JPA Settings
spring.jpa.generate-ddl:true
spring.jpa.hibernate.ddl-auto:update
#spring.jpa.hibernate.dialect:org.hibernate.dialect.H2Dialect
spring.jpa.properties.hibernate.format_sql:false
spring.jpa.show-sql:true

src/main/java/hello/Application.java

package hello;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}

}

创建实体

src/main/java/hello/domain/Book.java

package hello.domain;

import javax.persistence.*;
import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

@Entity
public class Book implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
private Integer id;

private String name;

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "BOOK_AUTHOR", joinColumns = {
@JoinColumn(name = "BOOK_ID", referencedColumnName = "ID")}, inverseJoinColumns = {
@JoinColumn(name = "AUTHOR_ID", referencedColumnName = "ID")})
private Set<Author> authors;

public Book() {
super();
}

public Book(String name) {
super();
this.name = name;
this.authors = new HashSet<>();
}

public Book(String name, Set<Author> authors) {
super();
this.name = name;
this.authors = authors;
}

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public Set<Author> getAuthors() {
return authors;
}

public void setAuthors(Set<Author> authors) {
this.authors = authors;
}

@Override
public String toString() {
return String.format("Book [id=%s, name=%s, authors=%s]", id, name, authors);
}

}

src/main/java/hello/domain/Author.java

package hello.domain;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import java.io.Serializable;
import java.util.Set;

@Entity
public class Author implements Serializable {

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue
private Integer id;

private String name;

@ManyToMany(mappedBy = "authors")
private Set<Book> books;

public Author() {
super();
}

public Author(String name) {
super();
this.name = name;
}

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public Set<Book> getBooks() {
return books;
}

public void setBooks(Set<Book> books) {
this.books = books;
}

@Override
public String toString() {
return String.format("Author [id=%s, name=%s, books=%s]", id, name, books);
}

}

创建 Repository

src/main/java/hello/repository/BookRepository.java

package hello.repository;

import hello.domain.Book;
import org.springframework.data.jpa.repository.JpaRepository;

import java.util.List;

public interface BookRepository extends JpaRepository<Book, Integer> {

Book findByName(String name);

List<Book> findByNameContaining(String name);

}

src/main/java/hello/repository/AuthorRepository.java

package hello.repository;

import hello.domain.Author;
import org.springframework.data.jpa.repository.JpaRepository;

import java.util.List;

public interface AuthorRepository extends JpaRepository<Author, Integer> {

Author findByName(String name);

List<Author> findByNameContaining(String name);

}

单元测试

编写单元测试

src/test/java/hello/BookRepositoryTests.java

package hello;

import hello.domain.Author;
import hello.domain.Book;
import hello.repository.AuthorRepository;
import hello.repository.BookRepository;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.Arrays;

import static org.assertj.core.api.Assertions.assertThat;

@RunWith(SpringRunner.class)
@DataJpaTest
public class BookRepositoryTests {

@Autowired
private BookRepository bookRepository;
@Autowired
private AuthorRepository authorRepository;

@Before
public void init() {
Author lewis = new Author("Lewis");
Author mark = new Author("Mark");
Author peter = new Author("Peter");

Book spring = new Book("Spring in Action");
spring.getAuthors().addAll(Arrays.asList(lewis, mark));

Book springboot = new Book("Spring Boot in Action");
springboot.getAuthors().addAll(Arrays.asList(lewis, peter));

bookRepository.save(Arrays.asList(spring, springboot));
}

@After
public void deleteAll() {
// 删除所有书籍，级联删除关联的作者，但是没有与书籍关联的作者不会被删掉
bookRepository.deleteAll();

// 删除所有作者，只能删除没有与书籍关联的作者，与书籍有关联的作者无法被删除
authorRepository.deleteAll();
}

@Test
public void findAll() {
assertThat(bookRepository.findAll()).hasSize(2);

assertThat(authorRepository.findAll()).hasSize(3);
}

@Test
public void findByName() {
assertThat(bookRepository.findByName("Spring in Action")).isNotNull();

assertThat(authorRepository.findByName("Lewis")).isNotNull();
}

@Test
public void findByNameContaining() {
assertThat(bookRepository.findByNameContaining("Spring")).hasSize(2);

assertThat(authorRepository.findByNameContaining("e")).hasSize(2);
}

@Test
public void margeBook() {
Book book = bookRepository.findByName("Spring in Action");
assertThat(book).isNotNull();

book.setName("Spring in Action (4th Edition)");
bookRepository.save(book);

assertThat(bookRepository.findByName("Spring in Action")).isNull();
assertThat(bookRepository.findByName("Spring in Action (4th Edition)")).isNotNull();
}

@Test
public void deleteBook() {
Book book = bookRepository.findByName("Spring Boot in Action");
assertThat(book).isNotNull();

bookRepository.delete(book);

assertThat(bookRepository.findAll()).hasSize(1);
assertThat(bookRepository.findByName("Spring Boot in Action")).isNull();

assertThat(authorRepository.findAll()).hasSize(2);
assertThat(authorRepository.findByName("Peter")).isNull();
}

@Test
public void plusAuthor() {
Book book = bookRepository.findByName("Spring in Action");
assertThat(book).isNotNull();

Author author = authorRepository.findByName("Jacob");
assertThat(author).isNull();

book.getAuthors().add(new Author("Jacob"));
bookRepository.save(book);

assertThat(bookRepository.findByName("Spring in Action").getAuthors()).hasSize(3);

assertThat(authorRepository.findAll()).hasSize(4);
assertThat(authorRepository.findByName("Jacob")).isNotNull();
}

@Test
public void clearAuthor() {
Book book = bookRepository.findByName("Spring in Action");
assertThat(book).isNotNull();

book.getAuthors().clear();
bookRepository.save(book);

assertThat(bookRepository.findAll()).hasSize(2);
assertThat(bookRepository.findByName("Spring in Action").getAuthors()).isEmpty();

assertThat(authorRepository.findAll()).hasSize(3);
}

@Test
public void removeAuthor() {
Book book = bookRepository.findByName("Spring Boot in Action");
assertThat(book).isNotNull();

Author author = authorRepository.findByName("Peter");
assertThat(author).isNotNull();

book.getAuthors().remove(author);
bookRepository.save(book);

assertThat(bookRepository.findAll()).hasSize(2);
assertThat(bookRepository.findByName("Spring Boot in Action").getAuthors()).hasSize(1);

assertThat(authorRepository.findAll()).hasSize(3);
assertThat(authorRepository.findByName("Peter")).isNotNull();
}

@Test
public void removeAllautors() {
Book book = bookRepository.findByName("Spring in Action");
assertThat(book).isNotNull();

book.getAuthors().removeAll(book.getAuthors());
bookRepository.save(book);

assertThat(bookRepository.findAll()).hasSize(2);
assertThat(bookRepository.findByName("Spring in Action").getAuthors()).isEmpty();

assertThat(authorRepository.findAll()).hasSize(3);
}

@Test
public void deleteAuthor() {
Author author = authorRepository.findByName("Peter");
assertThat(author).isNotNull();

authorRepository.delete(author);

assertThat(bookRepository.findAll()).hasSize(2);
assertThat(bookRepository.findByName("Spring in Action").getAuthors()).hasSize(2);
assertThat(bookRepository.findByName("Spring Boot in Action").getAuthors()).hasSize(2);

assertThat(authorRepository.findAll()).hasSize(3);
assertThat(authorRepository.findByName("Peter")).isNotNull();
}

@Test
public void deleteAllAuthors() {
authorRepository.deleteAll();

assertThat(bookRepository.findAll()).hasSize(2);
assertThat(bookRepository.findByName("Spring in Action").getAuthors()).hasSize(2);
assertThat(bookRepository.findByName("Spring Boot in Action").getAuthors()).hasSize(2);

assertThat(authorRepository.findAll()).hasSize(3);
}

}

执行测试用例

mvn clean test

资源